1. Gases Chapter 10/11 Modern Chemistry
Sections 10.1,
The Kinetic Molecular Theory of Matter
Gases and Pressure
The Gas Laws
Gas Volumes and the Ideal Gas Law
Chapter 8 Section 1 Describing Chemical Reactions p

2. Chapter 11Section 1 Gases & Pressure p. 361-368
Gases and Pressure
Chapter 11Section 1 Gases & Pressure p

3. Chapter 11Section 1 Gases & Pressure p. 361-368
Pressure = force (in Newtons) per unit area
Pressure of a gas is caused by particles of a gas colliding with the walls of its container
Pressure (P) of a gas depends on volume (V), temperature (T), and the number of particles (n).
Chapter 11Section 1 Gases & Pressure p

4. Pressure & Amount of Gas
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Chapter 11Section 1 Gases & Pressure p

5. Atomospheric Pressure
The atmosphere exerts pressure.
78% N, 21% O, 1% other
Atmospheric pressure is the sum of the individual pressures of the gases.
Chapter 11Section 1 Gases & Pressure p

6. Chapter 11Section 1 Gases & Pressure p. 361-368
Measuring Pressure
Barometer: a device used to measure atmospheric pressure.
Developed by Evangelista Torricelli in the early 1600s.
Chapter 11Section 1 Gases & Pressure p
p. 363

7. Chapter 11Section 1 Gases & Pressure p. 361-368
Mercury Barometer
Chapter 11Section 1 Gases & Pressure p
p. 363

8. Chapter 11Section 1 Gases & Pressure p. 361-368
Aneroid Barometer
The aneroid barometer is operated by a metal cell containing only a very small amount of air, or a series of such cells joined together. Increased air pressure causes the sides of the cell or cells to come closer together. One side is fixed to the base of the instrument while the other is connected by means of a system of levers and pulleys to a rotating pointer that moves over a scale on the face of the instrument.
Chapter 11Section 1 Gases & Pressure p

9. Chapter 11Section 1 Gases & Pressure p. 361-368
Measuring Pressure
A manometer measures the pressure of a gas in a flask.
Chapter 11Section 1 Gases & Pressure p
p. 363

10. Chapter 11Section 1 Gases & Pressure p. 361-368
Manometer
Chapter 11Section 1 Gases & Pressure p

11. Chapter 11Section 1 Gases & Pressure p. 361-368
Units of Pressure
The average atmospheric pressure at sea level at 0°C.
760 mm Hg – millimeters of mercury
1.00 atm – atmospheres
kPa – kilopascals (SI Units)
1 pascal is the pressure exerted by a force of 1 Newton acting on an area of 1 square meter
See the table on page 364
Chapter 11Section 1 Gases & Pressure p

12. Table 1 Units of Pressure
Chapter 11 Section 1 Gases & Pressure p
p. 364

13. Converting Pressure Units
The average atmospheric pressure in Denver, Colorado, is atm. Express this pressure in (a) millimeters of mercury (mm Hg) and (b) kilopascals (kPa).
p. 365
a. 631 mm Hg b kPa
Chapter 11Section 1 Gases & Pressure p

14. Chapter 11Section 1 Gases & Pressure p. 361-368
Practice Problems p. 365
Convert a pressure of 1.75 atm to kPa and to mm Hg.
The critical pressure of carbon dioxide is 72.7 atm. What is this value in units of pascals?
p. 365
177 kPa, 1330 mm Hg
× 106 Pa
Chapter 11Section 1 Gases & Pressure p

15. Dalton’s Law of Partial Pressures
Partial Pressure: The pressure of each gas in a mixture
Dalton’s Law of Partial Pressures: The total pressure of a gas mixture is the sum of the partial pressures of the component gases.
PT =
p1 +
p2 +
p3 …
Chapter 11Section 1 Gases & Pressure p

16. Chapter 11Section 1 Gases & Pressure p. 361-368
Partial Pressures
Chapter 11Section 1 Gases & Pressure p

17. Law of Partial Pressures
Chapter 11Section 1 Gases & Pressure p
p. 363

18. Gases Collected by Water Displacement
Chapter 11Section 1 Gases & Pressure p
p. 366

19. Gases Collected by Water Displacement
A gas collected over water is a mixture of the gas and water vapor
The pressure water exerts is called vapor pressure
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Chapter 11Section 1 Gases & Pressure p

20. Gases Collected by Water Displacement
When the water levels inside and outside the tube are the same the PT = Patm
Patm = pgas + pH2O or
pgas = Patm - pH2O
atm
atm
atm
atm
PT<Patm
PT=Patm
PT>Patm
Chapter 11Section 1 Gases & Pressure p

21. Gases Collected by Water Displacement
The vapor pressure of water varies with temp.
p. 859
Chapter 11Section 1 Gases & Pressure p

22. Chapter 11Section 1 Gases & Pressure p. 361-368
Dalton’s Law Problems
Oxygen gas from the decomposition of potassium chlorate, KClO3, was collected by water displacement. The barometric pressure and the temperature during the experiment were mm Hg and 20.0°C, respectively. What was the partial pressure of the oxygen collected?
p. 367
mm Hg
Chapter 11Section 1 Gases & Pressure p

23. Chapter 11Section 1 Gases & Pressure p. 361-368
Practice Problems p. 367
Some hydrogen gas is collected over water at 20.0°C.The levels of water inside and outside the gas-collection bottle are the same. The partial pressure of hydrogen is mm Hg.What is the barometric pressure at the time the gas is collected?
p. 367
mm Hg
Chapter 11Section 1 Gases & Pressure p

24. Chapter 11Section 1 Gases & Pressure p. 361-368
Ch 11 Sec 1 Homework
Page # 1-8
Chapter 11Section 1 Gases & Pressure p

25. Chapter 11Section 1 Gases & Pressure p. 361-368
Increasing Pressure
Insert Glencoe Chemistry Disc 2
Chapter 11Section 1 Gases & Pressure p

26. Chapter 11 Section 2 The Gas Laws p. 369-377
Boyle’s Law
TEMP.
TEMP.
PRESSURE
AMOUNT
AMOUNT
VOLUME
Chapter 11 Section 2 The Gas Laws p

27. Chapter 11 Section 2 The Gas Laws p. 369-377
Boyle’s Law
P & V relationship; n & T held constant
“The volume of a fixed mass of gas varies inversely with the pressure at constant temperature.”
Insert Glencoe Chemistry Matter Disc 2
Chapter 11 Section 2 The Gas Laws p
p. 369

28. Chapter 11 Section 2 The Gas Laws p. 369-377
Boyle’s Law
PV = k k is a constant
P1 V1 = k
P2 V2 = k
P1 V1 = P2 V2 V1 V2 P1 P2
Chapter 11 Section 2 The Gas Laws p
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29. Chapter 11 Section 2 The Gas Laws p. 369-377
Boyle’s Law Problem
A sample of oxygen gas has a volume of mL when its pressure is atm. What will the volume of the gas be at a pressure of atm if the temperature remains constant?
p. 370
mL O2
Chapter 11 Section 2 The Gas Laws p

30. Chapter 11 Section 2 The Gas Laws p. 369-377
Charles’ Law
TEMP.
PRESSURE
PRESSURE
AMOUNT
AMOUNT
VOLUME
Chapter 11 Section 2 The Gas Laws p

31. Kelvin Temperature Scale
Same size degrees as the Celcius scale
0 K = ° C
0 K = absolute zero
K = °C
Chapter 11 Section 2 The Gas Laws p

32. Chapter 11 Section 2 The Gas Laws p. 369-377
Charles’ Law
V & T relationship; n & P held constant
The volume of a fixed mass of gas at constant pressure varies directly with the Kelvin temperature.”
Insert Glencoe Chemistry Matter Disc 2
Chapter 11 Section 2 The Gas Laws p

33. Chapter 11 Section 2 The Gas Laws p. 369-377
Charles’ Law
V / T = k
k = a constant
V1 / T1 = k
V2 / T2 = k
V1 = V2
T1 = T2 V2 V1 T1 T2
Chapter 11 Section 2 The Gas Laws p
p. 372

34. Chapter 11 Section 2 The Gas Laws p. 369-377
Charles’ Law Problem
A sample of neon gas occupies a volume of 752 mL at 25°C. What volume will the gas occupy at 50°C if the pressure remains constant?
p. 372
mL Ne
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35. Chapter 11 Section 2 The Gas Laws p. 369-377
Combined Gas Law
TEMP.
PRESSURE
AMOUNT
AMOUNT
VOLUME
Chapter 11 Section 2 The Gas Laws p

36. Chapter 11 Section 2 The Gas Laws p. 369-377
Combined Gas Law
P, V and T relationship; n held constant
“The combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas.” P 1 V 1 P 2 V 2 = T 1 T 2
Chapter 11 Section 2 The Gas Laws p

37. Chapter 11 Section 2 The Gas Laws p. 369-377
STP
Standard Temperature and Pressure
Standard Pressure
1.00 atm
760 mm Hg
kPa
Standard Temperature
273 K
0° C
Chapter 11 Section 2 The Gas Laws p

38. Combined Gas Law Problems
A helium-filled balloon has a volume of 50.0 L at 25°C and 1.08 atm. What volume will it have at atm and 10.0°C?
p. 375
L He
Chapter 11 Section 2 The Gas Laws p